Integrated primary startup bias and MOSFET driver

1. A DC-to-DC converter, comprising: a power transformer having a primary side and a secondary side; a plurality of power transistors coupled to the primary side of the transformer; a secondary bias supply coupled to the secondary side of the transformer; and a secondary side controller coupled to the secondary side of the transformer and configured to generate a feedback control signal based on a voltage level associated with the secondary side of the transformer; further comprising an integrated transistor driver and pulse width modulation (PWM) controller that receives an input voltage of the DC-to-DC converter, and wherein, during startup, the secondary side controller receives operating power from the integrated transistor driver and PWM controller controlling the plurality of power transistors, but after startup, the secondary side controller instead receives operating power derived from an output voltage from the secondary side of the transformer; wherein the integrated transistor driver and PWM controller includes: a pulse generator that generates pulse signals to be used during startup to control the plurality of power transistors; and a plurality of switches, each switch selects either one of the pulse signals from the pulse generator or a gate drive control signal from the secondary side controller to control one of the power transistors; further comprising a PWM detect unit to detect a presence of the gate drive control signal from the secondary side controller and to cause the switches to be controlled on the basis of whether the gate drive control signal is detected; and wherein the PWM detect unit disables the pulse generator when detecting a presence of the gate drive control signal from the secondary side controller.

2. The DC-to-DC converter of claim 1 wherein the PWM detect unit causes an output to control the switches between two states, a first state, during startup, in which the power transistors are controlled by the pulse signals and a second state, after startup, in which the power transistors are controlled by the gate drive control signals from the secondary side controller.

3. The DC-to-DC converter of claim 1 wherein during startup the DC-to-DC converter operates in an unregulated fashion, but after startup, the DC-to-DC converter operates in a regulated fashion.

4. A DC-to-DC converter, comprising: a power transformer having a primary side and a secondary side; a plurality of power transistors coupled to the primary side of the transformer; a secondary side controller coupled to the secondary side of the transformer and configured to generate a gate drive control signal based on a voltage level associated with the secondary side of the transformer; and an integrated transistor driver and pulse width modulation (PWM) controller to receive the gate drive control signal from the secondary side controller and to selectively generate transistor control signals to the power transistors based on either the gate drive control signal from the secondary side controller or based on a pulse signal from an internal pulse generator; and wherein the integrated transistor driver and PWM controller comprises; a pulse generator to generate and provide a plurality of pulse signals to be used during startup to control the plurality of power transistors; a plurality of switches that selectively provide the gate drive control signal or a pulse signal from the pulse generator to the power transistors; a PWM detect unit to detect a presence of the gate drive control signal from the secondary side controller and to generate a detect signal that indicates whether the gate drive control signal has been detected; and an output control unit to control the switches based on the detect signal from the PWM detect unit.

5. The DC-to-DC converter of claim 4 wherein when the PWM detect unit detects a presence of the gate drive control signal from the secondary side controller, the PWM detect unit disables the pulse generator and generates a detect signal that indicates the gate drive control signal has been detected.

6. The DC-to-DC converter of claim 4 wherein the PWM detect unit causes an output to control the switches between two states, a first state, during startup, in which the power transistors are controlled by the pulse signals and a second state, after startup, in which the power transistors are controlled by the gate drive control signals from the secondary side controller.

7. The DC-to-DC converter of claim 4 wherein during startup the DC-to-DC converter operates in an unregulated fashion, but after startup, the DC-to-DC converter operates in a regulated fashion.